CN114736665B - Layer-by-layer self-assembled calcium oxide microcapsule and preparation method and application thereof - Google Patents
Layer-by-layer self-assembled calcium oxide microcapsule and preparation method and application thereof Download PDFInfo
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- CN114736665B CN114736665B CN202210376338.1A CN202210376338A CN114736665B CN 114736665 B CN114736665 B CN 114736665B CN 202210376338 A CN202210376338 A CN 202210376338A CN 114736665 B CN114736665 B CN 114736665B
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- calcium oxide
- sodium alginate
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- polyaldehyde
- chitosan
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- BRPQOXSCLDDYGP-UHFFFAOYSA-N calcium oxide Chemical compound [O-2].[Ca+2] BRPQOXSCLDDYGP-UHFFFAOYSA-N 0.000 title claims abstract description 217
- 239000000292 calcium oxide Substances 0.000 title claims abstract description 158
- ODINCKMPIJJUCX-UHFFFAOYSA-N calcium oxide Inorganic materials [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 title claims abstract description 158
- 239000003094 microcapsule Substances 0.000 title claims abstract description 82
- 238000002360 preparation method Methods 0.000 title claims abstract description 34
- 235000010413 sodium alginate Nutrition 0.000 claims abstract description 114
- 229940005550 sodium alginate Drugs 0.000 claims abstract description 114
- 239000000661 sodium alginate Substances 0.000 claims abstract description 114
- IXPNQXFRVYWDDI-UHFFFAOYSA-N 1-methyl-2,4-dioxo-1,3-diazinane-5-carboximidamide Chemical compound CN1CC(C(N)=N)C(=O)NC1=O IXPNQXFRVYWDDI-UHFFFAOYSA-N 0.000 claims abstract description 100
- 229920001744 Polyaldehyde Polymers 0.000 claims abstract description 82
- 229920001661 Chitosan Polymers 0.000 claims abstract description 43
- 238000006243 chemical reaction Methods 0.000 claims abstract description 31
- SJECZPVISLOESU-UHFFFAOYSA-N 3-trimethoxysilylpropan-1-amine Chemical compound CO[Si](OC)(OC)CCCN SJECZPVISLOESU-UHFFFAOYSA-N 0.000 claims abstract description 16
- 238000000034 method Methods 0.000 claims abstract description 16
- 239000011248 coating agent Substances 0.000 claims abstract description 9
- 238000000576 coating method Methods 0.000 claims abstract description 9
- 238000003756 stirring Methods 0.000 claims description 94
- 239000000243 solution Substances 0.000 claims description 71
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 67
- 238000001035 drying Methods 0.000 claims description 33
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 claims description 26
- JQWHASGSAFIOCM-UHFFFAOYSA-M sodium periodate Chemical compound [Na+].[O-]I(=O)(=O)=O JQWHASGSAFIOCM-UHFFFAOYSA-M 0.000 claims description 24
- NMJORVOYSJLJGU-UHFFFAOYSA-N methane clathrate Chemical compound C.C.C.C.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O NMJORVOYSJLJGU-UHFFFAOYSA-N 0.000 claims description 22
- 238000002156 mixing Methods 0.000 claims description 22
- 239000011259 mixed solution Substances 0.000 claims description 17
- 238000001914 filtration Methods 0.000 claims description 7
- 230000035484 reaction time Effects 0.000 claims description 7
- 238000001291 vacuum drying Methods 0.000 claims description 6
- 239000007864 aqueous solution Substances 0.000 claims description 5
- 239000002244 precipitate Substances 0.000 claims description 4
- 238000001556 precipitation Methods 0.000 claims description 4
- WGCNASOHLSPBMP-UHFFFAOYSA-N hydroxyacetaldehyde Natural products OCC=O WGCNASOHLSPBMP-UHFFFAOYSA-N 0.000 claims 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 abstract description 33
- 230000000694 effects Effects 0.000 abstract description 18
- 238000005553 drilling Methods 0.000 abstract description 9
- 230000036632 reaction speed Effects 0.000 abstract description 8
- 230000008569 process Effects 0.000 abstract description 5
- 238000004519 manufacturing process Methods 0.000 abstract description 4
- 230000009286 beneficial effect Effects 0.000 abstract description 3
- 239000003607 modifier Substances 0.000 abstract 1
- 239000010410 layer Substances 0.000 description 44
- 230000000052 comparative effect Effects 0.000 description 24
- 239000002245 particle Substances 0.000 description 13
- 239000006087 Silane Coupling Agent Substances 0.000 description 12
- 239000000725 suspension Substances 0.000 description 10
- 239000011257 shell material Substances 0.000 description 9
- 125000003172 aldehyde group Chemical group 0.000 description 7
- 239000007822 coupling agent Substances 0.000 description 7
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 6
- 238000000354 decomposition reaction Methods 0.000 description 6
- 238000010586 diagram Methods 0.000 description 6
- 238000010438 heat treatment Methods 0.000 description 6
- 229910052760 oxygen Inorganic materials 0.000 description 6
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 5
- 125000003277 amino group Chemical group 0.000 description 5
- 230000006196 deacetylation Effects 0.000 description 5
- 238000003381 deacetylation reaction Methods 0.000 description 5
- 239000006185 dispersion Substances 0.000 description 5
- 238000002474 experimental method Methods 0.000 description 5
- 230000004048 modification Effects 0.000 description 5
- 238000012986 modification Methods 0.000 description 5
- 229910052757 nitrogen Inorganic materials 0.000 description 5
- 230000001376 precipitating effect Effects 0.000 description 5
- 239000008213 purified water Substances 0.000 description 5
- 239000000376 reactant Substances 0.000 description 5
- 229910052710 silicon Inorganic materials 0.000 description 5
- 239000010703 silicon Substances 0.000 description 5
- BHPQYMZQTOCNFJ-UHFFFAOYSA-N Calcium cation Chemical compound [Ca+2] BHPQYMZQTOCNFJ-UHFFFAOYSA-N 0.000 description 4
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 4
- 239000011575 calcium Substances 0.000 description 4
- 229910052791 calcium Inorganic materials 0.000 description 4
- 229910052799 carbon Inorganic materials 0.000 description 4
- 238000000724 energy-dispersive X-ray spectrum Methods 0.000 description 4
- 230000005484 gravity Effects 0.000 description 4
- 230000002209 hydrophobic effect Effects 0.000 description 4
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 4
- 239000001301 oxygen Substances 0.000 description 4
- 238000012360 testing method Methods 0.000 description 4
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 3
- 230000008859 change Effects 0.000 description 3
- 239000013000 chemical inhibitor Substances 0.000 description 3
- 238000004132 cross linking Methods 0.000 description 3
- 238000009826 distribution Methods 0.000 description 3
- 238000005538 encapsulation Methods 0.000 description 3
- 238000005265 energy consumption Methods 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 239000012530 fluid Substances 0.000 description 3
- 238000002347 injection Methods 0.000 description 3
- 239000007924 injection Substances 0.000 description 3
- 230000009545 invasion Effects 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 230000035699 permeability Effects 0.000 description 3
- 239000011148 porous material Substances 0.000 description 3
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- 239000002262 Schiff base Substances 0.000 description 2
- 150000004753 Schiff bases Chemical class 0.000 description 2
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 description 2
- 239000000920 calcium hydroxide Substances 0.000 description 2
- 229910001861 calcium hydroxide Inorganic materials 0.000 description 2
- 239000011247 coating layer Substances 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 239000003112 inhibitor Substances 0.000 description 2
- 239000003345 natural gas Substances 0.000 description 2
- 239000012466 permeate Substances 0.000 description 2
- 238000001338 self-assembly Methods 0.000 description 2
- 239000011780 sodium chloride Substances 0.000 description 2
- 150000001298 alcohols Chemical class 0.000 description 1
- 150000001408 amides Chemical class 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 238000005253 cladding Methods 0.000 description 1
- 238000006482 condensation reaction Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 230000001186 cumulative effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000018044 dehydration Effects 0.000 description 1
- 238000006297 dehydration reaction Methods 0.000 description 1
- 230000003111 delayed effect Effects 0.000 description 1
- 238000011549 displacement method Methods 0.000 description 1
- 238000002149 energy-dispersive X-ray emission spectroscopy Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 235000019441 ethanol Nutrition 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 125000002485 formyl group Chemical group [H]C(*)=O 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 230000007062 hydrolysis Effects 0.000 description 1
- 238000006460 hydrolysis reaction Methods 0.000 description 1
- 125000001165 hydrophobic group Chemical group 0.000 description 1
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 1
- 229920006150 hyperbranched polyester Polymers 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- 239000008239 natural water Substances 0.000 description 1
- 238000003921 particle size analysis Methods 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 235000013855 polyvinylpyrrolidone Nutrition 0.000 description 1
- 229920000036 polyvinylpyrrolidone Polymers 0.000 description 1
- 239000001267 polyvinylpyrrolidone Substances 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 239000004576 sand Substances 0.000 description 1
- FZHAPNGMFPVSLP-UHFFFAOYSA-N silanamine Chemical compound [SiH3]N FZHAPNGMFPVSLP-UHFFFAOYSA-N 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 230000002195 synergetic effect Effects 0.000 description 1
Classifications
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
- C09K8/58—Compositions for enhanced recovery methods for obtaining hydrocarbons, i.e. for improving the mobility of the oil, e.g. displacing fluids
- C09K8/592—Compositions used in combination with generated heat, e.g. by steam injection
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J13/00—Colloid chemistry, e.g. the production of colloidal materials or their solutions, not otherwise provided for; Making microcapsules or microballoons
- B01J13/02—Making microcapsules or microballoons
- B01J13/06—Making microcapsules or microballoons by phase separation
- B01J13/14—Polymerisation; cross-linking
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B41/00—Equipment or details not covered by groups E21B15/00 - E21B40/00
- E21B41/0099—Equipment or details not covered by groups E21B15/00 - E21B40/00 specially adapted for drilling for or production of natural hydrate or clathrate gas reservoirs; Drilling through or monitoring of formations containing gas hydrates or clathrates
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/01—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells specially adapted for obtaining from underwater installations
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/16—Enhanced recovery methods for obtaining hydrocarbons
- E21B43/24—Enhanced recovery methods for obtaining hydrocarbons using heat, e.g. steam injection
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P90/00—Enabling technologies with a potential contribution to greenhouse gas [GHG] emissions mitigation
- Y02P90/70—Combining sequestration of CO2 and exploitation of hydrocarbons by injecting CO2 or carbonated water in oil wells
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- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Mining & Mineral Resources (AREA)
- Chemical & Material Sciences (AREA)
- Geology (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Fluid Mechanics (AREA)
- Physics & Mathematics (AREA)
- Environmental & Geological Engineering (AREA)
- Organic Chemistry (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Materials Engineering (AREA)
- Dispersion Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Manufacturing Of Micro-Capsules (AREA)
- Medicinal Preparation (AREA)
Abstract
The invention provides a layer-by-layer self-assembled calcium oxide microcapsule, and a preparation method and application thereof. Firstly, preparing a modified calcium oxide core by using a modifier 3-aminopropyl trimethoxy silane; and then sequentially coating the calcium oxide core with polyaldehyde sodium alginate, chitosan and polyaldehyde sodium alginate, thereby preparing the calcium oxide microcapsule. The calcium oxide microcapsule can effectively slow down the reaction speed and the heat release speed of calcium oxide and water, achieves the effect of delaying the reaction and the heat release, is easy to control the reaction and the heat release, can go deep into a reservoir, has high utilization efficiency and low cost, is beneficial to protecting the reservoir, improves the stability of a well wall in the drilling process, and improves the safety of the hydrate drilling and production process.
Description
Technical Field
The invention relates to the technical field of natural gas hydrate exploitation, in particular to a layer-by-layer self-assembled calcium oxide microcapsule, and a preparation method and application thereof.
Background
The natural gas hydrate is a cage-type crystal formed by gas and water under the conditions of low temperature and high pressure, is a high-efficiency clean energy source, and has great energy potential when more than 97% of the hydrate is distributed at the edge of the ocean continent, but the exploitation difficulty is also great. At present, the exploitation of the natural gas hydrate mainly changes the phase balance condition of the natural gas hydrate in a reservoir to convert the natural gas hydrate into natural gas and water, so that the effective exploitation of the natural gas hydrate is realized. The natural gas hydrate exploitation technology in the sea area of China comprises a depressurization method, a heating method and CO 2 Substitution and chemical inhibitor injection.
The depressurization method is to accelerate the decomposition of natural gas hydrate by reducing the formation pressure; although the method can solve the problems of complex structure well of shallow and soft stratum, single well yield improvement and the like, the method cannot effectively solve the problems of loose geology, unstable well wall caused by poor stratum cementation, natural gas yield reduction caused by sand production and the like of the deep water stratum. The heating method is to change the ambient temperature around the hydrate to promote the decomposition, mainly by using the drilling technology to install a pipeline in a natural gas hydrate stable layer, and injecting hot fluid to directly heat the hydrate stratum so as to decompose the natural gas hydrate; the technology has simple implementation and obvious effect, but has high cost, large energy consumption and difficult control of the decomposition speed. CO 2 The displacement method is carried out by CO 2 The natural gas hydrate is replaced and extracted in the hydrate phase, and the problems of low replacement speed, difficult regulation and control of the extraction speed and the like exist. The chemical inhibitor injection method is to inject chemical inhibitor (such as thermodynamic inhibitor including salts, alcohols, kinetic inhibitor including polyvinylpyrrolidone, hyperbranched polyester amide polymer, etc.) to change the phase balance condition of the hydrate or influence the stability of hydrate crystal nucleus, promote the decomposition of partial hydrate, but has high exploitation cost and high environmental pollution risk.
Calcium oxide is a white to gray solid, is an alkaline oxide, is sensitive to humidity, is easy to absorb carbon dioxide and moisture from air, reacts with water to generate calcium hydroxide and emits a large amount of heat, and can self-heat to promote the decomposition of natural gas hydrate; the resulting calcium hydroxide can maintain the pH environment alkaline. The calcium oxide is directly used for heating the stratum temperature to promote the decomposition of the natural gas hydrate, and has the defects of high reaction speed and heat release speed, high heat release temperature, difficulty in control and the like; and the reaction speed is high, so that the water is difficult to penetrate into a reservoir, and the utilization efficiency is low.
The present invention has been made to solve the above-described problems.
Disclosure of Invention
The invention aims to solve the technical problems of high cost, high energy consumption, difficult control of heat release and the like caused by injecting hot fluid by a heating method at present and the problems of high reaction speed and heat release speed, high heat release temperature, difficult control, low utilization efficiency and the like caused by independently adding calcium oxide. The calcium oxide microcapsule can effectively slow down the reaction speed and the heat release speed of calcium oxide and water, achieves the effect of delaying the reaction and the heat release, is easy to control the reaction and the heat release, can go deep into a reservoir, has high utilization efficiency and low cost, is beneficial to protecting the reservoir, improves the stability of a well wall in the drilling process, and improves the safety of the hydrate drilling and production process.
The technical scheme of the invention is as follows:
a layer-by-layer self-assembled calcium oxide microcapsule is prepared by sequentially coating multi-aldehyde sodium alginate, chitosan and multi-aldehyde sodium alginate on the surface of a modified calcium oxide core.
According to the invention, the modified calcium oxide core is prepared by modifying calcium oxide with a silane coupling agent 3-aminopropyl trimethoxy silane; the polyaldehyde sodium alginate is prepared by reacting sodium alginate and sodium periodate.
According to the present invention, the particle size of the calcium oxide microcapsule is preferably 1 to 360. Mu.m, and the particle size of the modified calcium oxide core is preferably 0.5 to 80. Mu.m.
The preparation method of the layer-by-layer self-assembled calcium oxide microcapsule comprises the following steps:
(1) Preparation of polyaldehyde sodium alginate
Mixing an absolute ethanol solution of sodium alginate and an aqueous solution of sodium periodate, and obtaining polyaldehyde sodium alginate through stirring reaction, ethylene glycol termination reaction, precipitation and precipitation, filtration and drying;
(2) Preparation of modified calcium oxide core
Mixing an absolute ethanol solution of 3-aminopropyl trimethoxy silane with calcium oxide, stirring, reacting, centrifuging and drying to obtain a modified calcium oxide core;
(3) Preparation of calcium oxide microcapsules
Mixing the modified calcium oxide core with an absolute ethanol solution of polyaldehyde sodium alginate, stirring, reacting, centrifuging and drying to obtain calcium oxide/polyaldehyde sodium alginate; mixing calcium oxide/polyaldehyde sodium alginate with an absolute ethanol solution of chitosan, and then stirring, reacting, centrifuging and drying to obtain calcium oxide/polyaldehyde sodium alginate/chitosan; and mixing the calcium oxide/polyaldehyde sodium alginate/chitosan and the anhydrous ethanol solution of polyaldehyde sodium alginate, stirring, reacting, centrifuging and drying to obtain the calcium oxide microcapsule.
According to the invention, in the step (1), the volume ratio of the mass of the sodium alginate to the absolute ethyl alcohol in the absolute ethyl alcohol solution of the sodium alginate is 1-5:5-25 g/mL.
According to a preferred embodiment of the present invention, in step (1), the concentration of the aqueous solution of sodium periodate is 0.02-0.5g/mL.
According to the invention, in step (1), the molar ratio of sodium periodate to sodium alginate structural units is preferably 0.3-0.6:1.
According to the invention, in the step (1), the stirring reaction temperature is room temperature, the stirring reaction time is 4-10 hours, and the stirring reaction condition is light-shielding.
According to the invention, in the step (1), the volume ratio of the mass of the sodium alginate to the ethylene glycol is 1-10:1-10 g/mL.
According to a preferred embodiment of the present invention, in step (1), the method for separating out the precipitate is as follows: adding the reaction solution into absolute ethyl alcohol so as to separate out a precipitate; the volume ratio of the reaction solution to the absolute ethyl alcohol is 1-10:5-50.
According to the present invention, in the step (1), the drying is preferably performed at 40 to 60 ℃.
According to the invention, in the step (2), the volume ratio of the 3-aminopropyl trimethoxysilane to the absolute ethanol in the absolute ethanol solution of the 3-aminopropyl trimethoxysilane is 1-5:50-100.
According to the invention, in the step (2), the mass ratio of the volume of the 3-aminopropyl trimethoxysilane to the mass of the calcium oxide is 1-10 mL:10-40g; preferably 1mL, 10-40g.
According to the invention, in the step (2), the stirring reaction temperature is 10-30 ℃, the stirring speed is 200-300 rpm, and the stirring reaction time is 10-60 minutes.
According to the invention, in the step (3), the concentration of the anhydrous ethanol solution of the polyaldehyde sodium alginate is 2-6 mg/mL.
According to a preferred embodiment of the invention, in step (3), the mass ratio of modified calcium oxide core to polyaldehyde sodium alginate is 30-100:1, preferably 50:1.
According to the preferred embodiment of the present invention, in the step (3), the modified calcium oxide core and the anhydrous ethanol solution of polyaldehyde sodium alginate are mixed and stirred for 10 to 20 minutes at room temperature at a stirring rate of 200 to 300rpm.
According to the invention, in the step (3), the mass concentration of the anhydrous ethanol solution of chitosan is preferably 2-6 mg/mL.
According to the invention, in the step (3), the mass ratio of the calcium oxide/polyaldehyde sodium alginate to the chitosan is preferably 30-100:1, preferably 50:1.
According to the preferred embodiment of the present invention, in the step (3), the reaction time of stirring after mixing the calcium oxide/polyaldehyde sodium alginate and the anhydrous ethanol solution of chitosan is 10 to 20 minutes, the reaction temperature of stirring is room temperature, and the stirring rate is 200 to 300rpm.
According to the invention, in the step (3), the mixed solution obtained by mixing the anhydrous ethanol solution of the calcium oxide/multi-aldehyde sodium alginate/chitosan and the multi-aldehyde sodium alginate has the mass ratio of 30-100:1, preferably 50:1.
According to the preferred embodiment of the present invention, in the step (3), the stirring reaction time is 10 to 20 minutes, the stirring reaction temperature is room temperature, and the stirring rate is 200 to 300rpm after the calcium oxide/polyaldehyde sodium alginate/chitosan and the polyaldehyde sodium alginate are mixed in the absolute ethanol solution.
According to the invention, in the steps (2) and (3), the centrifugal rotation speed is 6000-10000rpm, and the centrifugal time is 5-10 minutes; the drying temperature is 70-90 ℃ and the drying time is 5-30 minutes.
The application of the layer-by-layer self-assembled calcium oxide microcapsule is applied to exploitation of natural gas hydrate in sea areas.
The invention has the technical characteristics and beneficial effects that:
1. aiming at exploitation of natural gas hydrate in sea areas, the invention provides a layer-by-layer self-assembled calcium oxide microcapsule. Compared with the prior heating fluid injection, the natural gas hydrate can be decomposed by releasing a large amount of heat when the calcium oxide meets water, so that the heat loss is better supplemented, and the cost and the energy consumption are low; because the particle size of the self-porous material is smaller, the self-porous material has better permeability, the requirement on the porosity of the stratum is smaller, and the exploitation efficiency can be greatly improved.
2. The calcium oxide microcapsule takes calcium oxide as a core, and the reaction speed of the calcium oxide and water can be effectively reduced through the shells assembled layer by layer, so that the heat release speed and heat release temperature of the calcium oxide can be effectively controlled, and the calcium oxide microcapsule has a great effect on drilling and production of natural gas hydrate. In the drilling process, the calcium oxide microcapsule is instantly injected into a hydrate reservoir, the heat release of calcium oxide in natural gas hydrate is delayed, the balance of the reservoir is not damaged, the reservoir damage is further prevented, the stability of a well wall in the drilling process is improved, the positive significance of protecting the reservoir is generated, and the safety of the hydrate drilling process is improved.
3. The calcium oxide microcapsule mainly takes internal hydrophobic modified calcium oxide as a core; si (OH) formed by hydrolysis of aminosilane coupling agent 3 Hydrogen bond is formed with hydroxyl on the surface of calcium oxide, and dehydration condensation reaction occursAnd (3) generating a-Si-O-R (R is calcium oxide) covalent bond, and grafting a hydrophobic group of the silane coupling agent onto the surface of the calcium oxide to form a coating cover, so as to obtain the modified calcium oxide with hydrophobicity. The surface of the calcium oxide core is modified by the silane coupling agent to have hydrophobicity, so that the contact between water molecules and the calcium oxide can be blocked, and the modified calcium oxide can maintain the self stability in water for a long time; experiments prove that the modified calcium oxide can be maintained for about half an hour in 3.5% saline water to start exothermic. The modified calcium oxide is further wrapped layer by layer to serve as an outer shell, and the microcapsule shell structure is a protective film with lower permeability, so that the invasion rate of water molecules can be obviously reduced, the reaction rate of the water molecules and the calcium oxide is reduced, and the heat release of the calcium oxide caused by the invasion of external water is reduced. The core and the shell in the calcium oxide microcapsule exert synergistic effect to realize long-acting blocking of water molecule invasion, can effectively slow down the reaction speed and the heat release speed of calcium oxide and water, achieve the effect of delaying the reaction and the heat release, and is easy to control the reaction and the heat release. In addition, the calcium oxide microcapsule reacts with water slowly, so that the calcium oxide microcapsule can go deep into a reservoir, and the utilization efficiency of the calcium oxide microcapsule is improved.
4. The layer-by-layer self-assembled calcium oxide microcapsule provided by the invention has the advantages of low cost, easily obtained preparation raw materials, mild reaction conditions, convenience for delaying the heat release of calcium oxide, and great significance for the exploitation of natural gas hydrate, and has a prospect of large-scale industrial production.
5. The invention modifies the amino group on the surface of the calcium oxide core and the aldehyde group of the multi-aldehyde sodium alginate, the aldehyde group of the calcium oxide/multi-aldehyde sodium alginate, the amino group in the chitosan, the amino group in the calcium oxide/multi-aldehyde sodium alginate/chitosan and the aldehyde group in the multi-aldehyde sodium alginate, and realizes the connection and the cladding between the core and the shell through a Schiff base self-assembly mechanism. The aldehyde groups on the multi-aldehyde sodium alginate react with the amino groups on the 3-aminopropyl-3-methoxy silane to form crosslinking points, the greater the concentration of the aldehyde groups is, the more crosslinking points are, and the better the wrapping effect of forming a reticular crosslinking structure is; if the core is directly coated with sodium alginate, the sodium alginate does not contain aldehyde functional groups, so that the self-assembly principle of Schiff base cannot be realized by direct coating, and the coating efficiency and effect of the shell material on the surface of calcium oxide are reduced. The sequence of each layer of the shell has strict requirements, the layers are required to be connected according to the sequence of aldehyde groups, amino groups and aldehyde groups, the wrapping effect of the microcapsule can be reduced by reversing the sequence, the microcapsule cannot be fully reacted and adsorbed with modified calcium oxide, the permeability of water is increased, and the effects of delaying the reaction speed of calcium oxide and water and the like cannot be achieved. The special preparation method of the shell layer ensures that the microcapsule has better encapsulation effect.
Drawings
FIG. 1 is a particle size distribution chart (a) and a cumulative particle size distribution chart of samples obtained in example 2, comparative example 1 and comparative example 3
(b)。
Fig. 2 is an EDS spectrum peak pattern diagram of the samples prepared in comparative example 1 (a), comparative example 2 (b), example 2 (c), and mass fraction diagram (d) of Ca, C, O, si and N in the samples.
FIG. 3 is a graph showing the temperature change during the reaction of the samples prepared in example 2 and comparative examples 1 to 4.
Detailed Description
The invention is further illustrated, but not limited, by the following examples.
Meanwhile, the experimental methods described in the following examples are all conventional methods unless otherwise specified; the reagents, materials, and apparatus, unless otherwise specified, are all commercially available.
Example 1
A preparation method of a layer-by-layer self-assembled calcium oxide microcapsule comprises the following steps:
(a) Preparation of polyaldehyde sodium alginate
i. 10g of sodium alginate was dispersed in 50mL of absolute ethanol to prepare suspension I.
ii. Solution II was prepared by dissolving 5.404g of sodium periodate in 50mL of purified water.
And iii, adding the solution II into the suspension I, magnetically stirring for 6 hours at room temperature in a dark place, and then adding 3.5mL of ethylene glycol to terminate the reaction.
iv, adding 100mL of reactant into 500mL of absolute ethyl alcohol, precipitating and filtering, and vacuum drying at 40 ℃ to obtain polyaldehyde sodium alginate.
(b) Preparation of modified calcium oxide core
i. 1mL of 3-aminopropyl trimethoxysilane was uniformly mixed with 100mL of absolute ethanol at 25℃to obtain a silane coupling agent solution.
ii. Uniformly mixing 10g of calcium oxide with the coupling agent solution in the step i, stirring for 10 minutes at room temperature under the condition of stirring speed of 200r/min, centrifuging the obtained solution at 8000rpm for 5 minutes, and drying at 70-90 ℃ for 10 minutes to obtain the modified calcium oxide core.
(c) Preparation of calcium oxide microcapsules
i. 0.2g of polyaldehyde sodium alginate is dissolved in 100mL of absolute ethanol and stirred for dispersion.
ii. Adding 20g of modified calcium oxide core in the step (b) into the mixed solution of the step (i) to be uniformly dispersed, stirring for 10 minutes at room temperature under the condition of stirring speed of 200r/min, centrifuging the obtained solution at 8000rpm for 5 minutes, and drying at 70-90 ℃ for 10 minutes to obtain a layer of coated calcium oxide microcapsule, namely calcium oxide/polyaldehyde sodium alginate.
iii, dissolving 0.2g chitosan (the deacetylation degree is more than or equal to 99.5%) in 100mL absolute ethanol, stirring and dispersing.
iv, adding 20g of calcium oxide/polyaldehyde sodium alginate in ii into the mixed solution in iii, uniformly dispersing, stirring for 10 minutes at room temperature under the condition of stirring speed of 200r/min, centrifuging the obtained solution at 8000rpm for 5 minutes, and drying at 70-90 ℃ for 10 minutes to obtain the two-layer coated calcium oxide microcapsule, namely the calcium oxide/polyaldehyde sodium alginate/chitosan.
v, dissolving 0.2g of polyaldehyde sodium alginate in 100mL of absolute ethyl alcohol, and stirring for dispersion.
vi, adding 20g of calcium oxide/polyaldehyde sodium alginate/chitosan in iv into the mixed solution in v, uniformly dispersing, stirring for 10 minutes at room temperature under the condition of stirring speed of 200r/min, centrifuging the obtained solution for 5 minutes at 8000rpm, and drying for 10 minutes at 70-90 ℃ to obtain the three-layer coated calcium oxide microcapsule.
Example 2
A preparation method of a layer-by-layer self-assembled calcium oxide microcapsule comprises the following steps:
(a) Preparation of polyaldehyde sodium alginate
i. 10g of sodium alginate was dispersed in 50mL of absolute ethanol to prepare suspension I.
ii. Solution II was prepared by dissolving 5.404g of sodium periodate in 50mL of purified water.
And iii, adding the solution II into the suspension I, magnetically stirring for 6 hours at room temperature in a dark place, and then adding 3.5mL of ethylene glycol to terminate the reaction.
iv, adding 100mL of reactant into 500mL of absolute ethyl alcohol, precipitating and filtering, and vacuum drying at 40 ℃ to obtain polyaldehyde sodium alginate.
(b) Preparation of modified calcium oxide core
i. 1mL of 3-aminopropyl trimethoxysilane was uniformly mixed with 100mL of absolute ethanol at 25℃to obtain a silane coupling agent solution.
ii. Uniformly mixing 20g of calcium oxide with the coupling agent solution in the step i, stirring for 40 minutes at room temperature under the condition of stirring speed of 200r/min, centrifuging the obtained solution at 8000rpm for 5 minutes, and drying at 70-90 ℃ for 10 minutes to obtain the modified calcium oxide core.
(c) Preparation of calcium oxide microcapsules
i. 0.4g of polyaldehyde sodium alginate was dissolved in 100mL of absolute ethanol and dispersed with stirring.
ii. Adding 20g of modified calcium oxide core in the step (b) into the mixed solution of the step (i) to be uniformly dispersed, stirring for 10 minutes at room temperature under the condition of stirring speed of 200r/min, centrifuging the obtained solution at 8000rpm for 5 minutes, and drying at 70-90 ℃ for 10 minutes to obtain a layer of coated calcium oxide microcapsule, namely calcium oxide/polyaldehyde sodium alginate.
iii, dissolving 0.4g chitosan (the deacetylation degree is more than or equal to 99.5%) in 100mL absolute ethanol, stirring and dispersing.
iv, adding 20g of calcium oxide/polyaldehyde sodium alginate in ii into the mixed solution in iii, uniformly dispersing, stirring for 10 minutes at room temperature under the condition of stirring speed of 200r/min, centrifuging the obtained solution at 8000rpm for 5 minutes, and drying at 70-90 ℃ for 10 minutes to obtain the two-layer coated calcium oxide microcapsule, namely the calcium oxide/polyaldehyde sodium alginate/chitosan.
v, dissolving 0.4g of polyaldehyde sodium alginate in 100mL of absolute ethyl alcohol, and stirring for dispersion.
vi, adding 20g of calcium oxide/polyaldehyde sodium alginate/chitosan in iv into the mixed solution in v, uniformly dispersing, stirring for 10 minutes at room temperature under the condition of stirring speed of 200r/min, centrifuging the obtained solution for 5 minutes at 8000rpm, and drying for 10 minutes at 70-90 ℃ to obtain the three-layer coated calcium oxide microcapsule.
Example 3
A preparation method of a layer-by-layer self-assembled calcium oxide microcapsule comprises the following steps:
(a) Preparation of polyaldehyde sodium alginate
i. 10g of sodium alginate was dispersed in 50mL of absolute ethanol to prepare suspension I.
ii. Solution II was prepared by dissolving 5.404g of sodium periodate in 50mL of purified water.
And iii, adding the solution II into the suspension I, magnetically stirring for 6 hours at room temperature in a dark place, and then adding 3.5mL of ethylene glycol to terminate the reaction.
iv, adding 100mL of reactant into 500mL of absolute ethyl alcohol, precipitating and filtering, and vacuum drying at 40 ℃ to obtain polyaldehyde sodium alginate.
(b) Preparation of modified calcium oxide core
i. 1mL of 3-aminopropyl trimethoxysilane was uniformly mixed with 100mL of absolute ethanol at 25℃to obtain a silane coupling agent solution.
ii. Uniformly mixing 40g of calcium oxide with the coupling agent solution in the step i, stirring for 40 minutes at room temperature under the condition of stirring speed of 300r/min, centrifuging the obtained solution at 9000rpm for 10 minutes, and drying at 70-90 ℃ for 20 minutes to obtain the modified calcium oxide core.
(c) Preparation of calcium oxide microcapsules
i. 0.6g of polyaldehyde sodium alginate was dissolved in 100mL of absolute ethanol and dispersed with stirring.
ii. Adding 20g of modified calcium oxide core in the step (b) into the mixed solution of the step (i) to be uniformly dispersed, stirring for 20 minutes at room temperature under the condition of stirring speed of 300r/min, centrifuging the obtained solution at 9000rpm for 10 minutes, and drying at 70-90 ℃ for 20 minutes to obtain a layer of coated calcium oxide microcapsule, namely calcium oxide/polyaldehyde sodium alginate.
iii, dissolving 0.6g chitosan (the deacetylation degree is more than or equal to 99.5%) in 100mL absolute ethanol, stirring and dispersing.
iv, adding 20g of calcium oxide/polyaldehyde sodium alginate in ii into the mixed solution in iii, uniformly dispersing, stirring for 20 minutes at room temperature under the condition of stirring speed of 300r/min, centrifuging the obtained solution at 9000rpm for 10 minutes, and drying at 70-90 ℃ for 20 minutes to obtain the two-layer coated calcium oxide microcapsule, namely the calcium oxide/polyaldehyde sodium alginate/chitosan.
v, dissolving 0.6g of polyaldehyde sodium alginate in 100mL of absolute ethyl alcohol, and stirring for dispersion.
vi, adding 20g of calcium oxide/polyaldehyde sodium alginate/chitosan in iv into the mixed solution in v, uniformly dispersing, stirring for 20 minutes at room temperature under the condition of stirring speed of 300r/min, centrifuging the obtained solution at 9000rpm for 10 minutes, and drying at 70-90 ℃ for 20 minutes to obtain the three-layer coated calcium oxide microcapsule.
Comparative example 1
Pure calcium oxide without modification and encapsulation.
Comparative example 2
A preparation method of modified calcium oxide comprises the following steps:
i. 1mL of 3-aminopropyl trimethoxysilane was uniformly mixed with 100mL of absolute ethanol at 25℃to obtain a silane coupling agent solution.
ii. Uniformly mixing 20g of calcium oxide with the coupling agent solution in the step i, stirring for 40 minutes at room temperature under the condition of stirring speed of 200r/min, centrifuging the obtained solution at 8000rpm for 5 minutes, and drying at 70-90 ℃ for 10 minutes to obtain the modified calcium oxide core.
Comparative example 3
The preparation method of the two-layer coated calcium oxide microcapsule comprises the following steps:
(a) Preparation of polyaldehyde sodium alginate
i. 10g of sodium alginate was dispersed in 50mL of absolute ethanol to prepare suspension I.
ii. Solution II was prepared by dissolving 5.404g of sodium periodate in 50mL of purified water.
And iii, adding the solution II into the suspension I, magnetically stirring for 6 hours at room temperature in a dark place, and then adding 3.5mL of ethylene glycol to terminate the reaction.
iv, adding 100mL of reactant into 500mL of absolute ethyl alcohol, precipitating and filtering, and vacuum drying at 40 ℃ to obtain polyaldehyde sodium alginate.
(b) Preparation of modified calcium oxide core
i. 1mL of 3-aminopropyl trimethoxysilane was uniformly mixed with 100mL of absolute ethanol at 25℃to obtain a silane coupling agent solution.
ii. Uniformly mixing 20g of calcium oxide with the coupling agent solution in the step i, stirring for 40 minutes at room temperature under the condition of stirring speed of 200r/min, centrifuging the obtained solution at 8000rpm for 5 minutes, and drying at 70-90 ℃ for 10 minutes to obtain the modified calcium oxide core.
(c) Preparation of calcium oxide microcapsules
i. 0.4g of polyaldehyde sodium alginate was dissolved in 100mL of absolute ethanol and dispersed with stirring.
ii. Adding 20g of modified calcium oxide core in the step (b) into the mixed solution of the step (i) to be uniformly dispersed, stirring for 10 minutes at room temperature under the condition of stirring speed of 200r/min, centrifuging the obtained solution at 8000rpm for 5 minutes, and drying at 70-90 ℃ for 10 minutes to obtain a layer of coated calcium oxide microcapsule, namely calcium oxide/polyaldehyde sodium alginate.
iii, dissolving 0.4g chitosan (the deacetylation degree is more than or equal to 99.5%) in 100mL absolute ethanol, stirring and dispersing.
iv, adding 20g of calcium oxide/polyaldehyde sodium alginate in ii into the mixed solution in iii, uniformly dispersing, stirring for 10 minutes at room temperature under the condition of stirring speed of 200r/min, centrifuging the obtained solution at 8000rpm for 5 minutes, and drying at 70-90 ℃ for 10 minutes to obtain the two-layer coated calcium oxide microcapsule, namely the calcium oxide/polyaldehyde sodium alginate/chitosan.
Comparative example 4
The preparation method of the three-layer coated unmodified calcium oxide microcapsule comprises the following steps:
(a) Preparation of polyaldehyde sodium alginate
i. 10g of sodium alginate was dispersed in 50mL of absolute ethanol to prepare suspension I.
ii. Solution II was prepared by dissolving 5.404g of sodium periodate in 50mL of purified water.
And iii, adding the solution II into the suspension I, magnetically stirring for 6 hours at room temperature in a dark place, and then adding 3.5mL of ethylene glycol to terminate the reaction.
iv, adding 100mL of reactant into 500mL of absolute ethyl alcohol, precipitating and filtering, and vacuum drying at 40 ℃ to obtain polyaldehyde sodium alginate.
(b) Preparation of calcium oxide microcapsules
i. 0.4g of polyaldehyde sodium alginate was dissolved in 100mL of absolute ethanol and dispersed with stirring.
ii. Adding 20g of calcium oxide core in the step (b) into the mixed solution of the step (i) to be uniformly dispersed, stirring for 10 minutes at room temperature under the condition of stirring speed of 200r/min, centrifuging the obtained solution at 8000rpm for 5 minutes, and drying at 70-90 ℃ for 10 minutes to obtain an unmodified layer of coated calcium oxide microcapsule, namely calcium oxide/polyaldehyde sodium alginate.
iii, dissolving 0.4g chitosan (the deacetylation degree is more than or equal to 99.5%) in 100mL absolute ethanol, stirring and dispersing.
iv, adding 20g of calcium oxide/polyaldehyde sodium alginate in ii into the mixed solution in iii, uniformly dispersing, stirring for 10 minutes at room temperature under the condition of stirring speed of 200r/min, centrifuging the obtained solution at 8000rpm for 5 minutes, and drying at 70-90 ℃ for 10 minutes to obtain the unmodified two-layer coated calcium oxide microcapsule, namely the calcium oxide/polyaldehyde sodium alginate/chitosan.
v, dissolving 0.4g of polyaldehyde sodium alginate in 100mL of absolute ethyl alcohol, and stirring for dispersion.
vi, adding 20g of calcium oxide/polyaldehyde sodium alginate/chitosan in iv into the mixed solution in v, uniformly dispersing, stirring for 10 minutes at room temperature under the condition of stirring speed of 200r/min, centrifuging the obtained solution for 5 minutes at 8000rpm, and drying for 10 minutes at 70-90 ℃ to obtain the unmodified three-layer coated calcium oxide microcapsule.
Test example 1
The calcium oxide microcapsules prepared in example 2, the calcium oxide in comparative example 1, the modified calcium oxide in comparative example 2, the two-layer coated calcium oxide microcapsules (calcium oxide/polyaldehyde sodium alginate/chitosan) in comparative example 3, and the three-layer coated unmodified calcium oxide microcapsules prepared in comparative example 4 were subjected to performance evaluation by the following experimental methods:
1. particle size testing:
the particle sizes of the calcium oxide in comparative example 1, the two-layer coated calcium oxide microcapsule (calcium oxide/polyaldehyde sodium alginate/chitosan) in comparative example 3, and the calcium oxide microcapsule prepared in example 2 in absolute ethanol were analyzed, respectively, using a laser particle size analyzer. The specific method comprises the following steps: and uniformly dispersing the sample in absolute ethyl alcohol, and dripping the sample into a laser particle size analyzer for particle size analysis.
FIG. 1 is the results of the absolute ethanol particle size test of the samples. The figure clearly shows the volume fraction ratio of different particle sizes in the calcium oxide microcapsules in the sample, and the microcapsules in a large particle size range occupy a relatively large volume fraction in three curves along with the increase of the number of coating layers. The particle size distribution range of the calcium oxide microcapsule is increased from 0.49-76 μm to 0.523-352 μm in comparative example 1, which shows that the coating effect is good.
EDS analysis
EDS test was performed on the calcium oxide microcapsules prepared in example 2, the calcium oxide in comparative example 1, and the modified calcium oxide in comparative example 2, and the results are shown in fig. 2.
Fig. 2 (a) is an EDS spectrum peak pattern diagram of the calcium oxide in comparative example 1, (b) is an EDS spectrum peak pattern diagram of the modified calcium oxide in comparative example 2, (c) is an EDS spectrum peak pattern diagram of the calcium oxide microcapsule prepared in example 1, and (d) is a mass fraction diagram of Ca, C, O, si and N.
From EDS energy spectrum, the main components in the calcium oxide are oxygen element and calcium element, and the peak value of the calcium and oxygen element in (a) is also verified. The calcium element is reduced when the modified calcium oxide is obtained, and the silicon element starts to rise and occupies a main proportion, so that the silicon element is related to the silane coupling agent used in the modification, and the silicon coupling agent is further verified to have ideal modification effect, and the nitrogen element which is also first appears in the modified calcium oxide is related to the nitrogen element in the silane coupling agent of the modified material; (b) In the figure, the peak values of oxygen and calcium elements are reduced, the peak value of silicon element is increased, and the peak value of nitrogen element is generated, so that the modification of the calcium oxide by the silane coupling agent is proved. Then, the calcium element in the three-layer coated modified calcium oxide occupies smaller specific gravity, the carbon element occupies maximum specific gravity, and the oxygen and silicon are coated in multiple layers, so that the specific gravity of the calcium element in the calcium oxide microcapsule is reduced, and the specific gravity of the carbon element in the calcium oxide microcapsule is increased due to the coating of the polyaldehyde sodium alginate and the chitosan due to the modification of the silane coupling agent; the invention successfully realizes multi-layer encapsulation of multi-aldehyde sodium alginate and chitosan.
3. Experiment of Heat-relieving Effect
The slow heat effect experiment was performed on the calcium oxide microcapsule prepared in example 2, the calcium oxide in comparative example 1, the modified calcium oxide prepared in comparative example 2, the two-layer coated calcium oxide microcapsule prepared in comparative example 3, and the three-layer coated non-modified calcium oxide microcapsule prepared in comparative example 4: 6g of the sample is added into 3.5wt% sodium chloride aqueous solution, and temperature data of the solution near the sample at each moment is recorded by an instrument built-in temperature sensor, so that the condition of the slow heating effect is judged.
Fig. 3 shows the temperature profile of the calcium oxide and microcapsules, and it is seen from the results that the calcium oxide has completely released all heat to peak within 20 minutes of water. The modified calcium oxide can still be maintained for about half an hour to start to react with water, and the temperature is increased sharply, so that the good hydrophobic property of the modified calcium oxide is shown. Compared with the prior art, the temperature of the three-layer coated unmodified calcium oxide microcapsule begins to increase after contacting with water, because the shell material serving as a permeable membrane can only delay and reduce the water flow, and can not physically block the water flow; and the heat release time of two hours and thirty minutes can be maintained, the effect of the modified calcium oxide can not be achieved, and the hydrophobic property of the modified calcium oxide is further proved. The hydrophobic property of the modified calcium oxide is the reason that the calcium oxide microcapsule of the invention can maintain the non-heat release in water for a long time; part of water gradually permeates into the modified calcium oxide along with the time, and reacts with the water to release heat, and the temperature rises along with the temperature, but the peak value of the calcium oxide is not high, so that the hydrophobicity of the modified calcium oxide is better. With the increase of the coating layers, the heat release time of the calcium oxide microcapsule is gradually prolonged, the heat release temperature is also gradually reduced, the temperature is the lowest when the three layers are coated, and the coating effect is the best. Although the calcium oxide encapsulates the multi-layer shell, some water still permeates into the core through the pores, and a slight increase in temperature occurs at the initial time.
Therefore, the calcium oxide microcapsule has good heat-relieving effect, is extremely compatible with the exploitation of the natural gas hydrate in the current sea area, has low cost and wide material sources, meets the environmental protection requirement of the exploitation, and has good application prospect in the exploitation of the natural gas hydrate.
Claims (6)
1. The application of the layer-by-layer self-assembled calcium oxide microcapsule is applied to exploitation of natural gas hydrate in sea areas;
the calcium oxide microcapsule is prepared by sequentially coating polyaldehyde sodium alginate, chitosan and polyaldehyde sodium alginate on the surface of a modified calcium oxide core; the grain diameter of the calcium oxide microcapsule is 1-360 mu m, and the grain diameter of the modified calcium oxide core is 0.5-80 mu m;
the preparation method of the layer-by-layer self-assembled calcium oxide microcapsule comprises the following steps:
(1) Preparation of polyaldehyde sodium alginate
Mixing an absolute ethanol solution of sodium alginate and an aqueous solution of sodium periodate, and obtaining polyaldehyde sodium alginate through stirring reaction, ethylene glycol termination reaction, precipitation and precipitation, filtration and drying;
the molar ratio of the sodium periodate to the sodium alginate structural unit is 0.3-0.6:1;
(2) Preparation of modified calcium oxide core
Mixing an absolute ethanol solution of 3-aminopropyl trimethoxy silane with calcium oxide, stirring, reacting, centrifuging and drying to obtain a modified calcium oxide core;
the mass ratio of the volume of the 3-aminopropyl trimethoxy silane to the mass ratio of the calcium oxide is 1-10 mL:10-40g;
(3) Preparation of calcium oxide microcapsules
Mixing the modified calcium oxide core with an absolute ethanol solution of polyaldehyde sodium alginate, stirring, reacting, centrifuging and drying to obtain calcium oxide/polyaldehyde sodium alginate; mixing calcium oxide/polyaldehyde sodium alginate with an absolute ethanol solution of chitosan, and then stirring, reacting, centrifuging and drying to obtain calcium oxide/polyaldehyde sodium alginate/chitosan; mixing the calcium oxide/polyaldehyde sodium alginate/chitosan and the anhydrous ethanol solution of polyaldehyde sodium alginate, stirring, reacting, centrifuging, and drying to obtain calcium oxide microcapsule;
the mass ratio of the modified calcium oxide core to the polyaldehyde sodium alginate is 30-100:1; the mass ratio of the calcium oxide/polyaldehyde sodium alginate to the chitosan is 30-100:1; in the mixed solution obtained by mixing the anhydrous ethanol solution of the calcium oxide/multi-aldehyde sodium alginate/chitosan and the multi-aldehyde sodium alginate, the mass ratio of the calcium oxide/multi-aldehyde sodium alginate/chitosan to the multi-aldehyde sodium alginate is 30-100:1.
2. The use of layer-by-layer self-assembled calcium oxide microcapsules according to claim 1, wherein in step (1) one or more of the following conditions are included:
i. in the absolute ethyl alcohol solution of sodium alginate, the volume ratio of the mass of the sodium alginate to the absolute ethyl alcohol is 1-5:5-25 g/mL;
ii. The concentration of the aqueous solution of sodium periodate is 0.02-0.5g/mL;
iii, stirring reaction temperature is room temperature, stirring reaction time is 4-10 hours, and stirring reaction conditions are light-shielding;
iv, the volume ratio of the mass of the sodium alginate to the glycol is 1-10:1-10 g/mL;
v, the method for separating out the precipitate is as follows: adding the reaction solution into absolute ethyl alcohol so as to separate out a precipitate; the volume ratio of the reaction solution to the absolute ethyl alcohol is 1-10:5-50;
vi, drying is vacuum drying at 40-60 ℃.
3. The use of layer-by-layer self-assembled calcium oxide microcapsules according to claim 1, characterized in that in step (2) one or more of the following conditions are included:
i. in the absolute ethyl alcohol solution of the 3-aminopropyl trimethoxy silane, the volume ratio of the 3-aminopropyl trimethoxy silane to the absolute ethyl alcohol is 1-5:50-100;
ii. The mass ratio of the volume of the 3-aminopropyl trimethoxysilane to the mass of the calcium oxide is 1mL to 10-40g;
iii, stirring reaction temperature is 10-30 ℃, stirring speed is 200-300 rpm, and stirring reaction time is 10-60 minutes.
4. The use of layer-by-layer self-assembled calcium oxide microcapsules according to claim 1, characterized in that in step (3) one or more of the following conditions are included:
i. the concentration of the absolute ethanol solution of the polyaldehyde sodium alginate is 2-6 mg/mL;
ii. The mass ratio of the modified calcium oxide core to the polyaldehyde sodium alginate is 50:1;
iii, mixing the modified calcium oxide core and the anhydrous ethanol solution of the polyaldehyde sodium alginate, stirring and reacting for 10-20 minutes, wherein the stirring and reacting temperature is room temperature, and the stirring speed is 200-300 rpm.
5. The use of layer-by-layer self-assembled calcium oxide microcapsules according to claim 1, characterized in that in step (3) one or more of the following conditions are included:
i. the mass concentration of the absolute ethyl alcohol solution of the chitosan is 2-6 mg/mL;
ii. The mass ratio of the calcium oxide/polyaldehyde sodium alginate to the chitosan is 50:1;
iii, mixing the calcium oxide/polyaldehyde sodium alginate and the absolute ethanol solution of chitosan, stirring for reaction time of 10-20 minutes, stirring for reaction temperature of room temperature and stirring speed of 200-300 rpm.
6. The use of layer-by-layer self-assembled calcium oxide microcapsules according to claim 1, characterized in that in step (3) one or more of the following conditions are included:
i. mixing the calcium oxide/polyaldehyde sodium alginate/chitosan and the anhydrous ethanol solution of polyaldehyde sodium alginate to obtain a mixed solution, wherein the mass ratio of the calcium oxide/polyaldehyde sodium alginate/chitosan to polyaldehyde sodium alginate is 50:1;
ii. Mixing the anhydrous ethanol solution of calcium oxide/polyaldehyde sodium alginate/chitosan and polyaldehyde sodium alginate, stirring for 10-20 min, stirring at room temperature and stirring speed of 200-300 rpm.
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